A lightsaber is kind of like a sword, but instead of having a blade made out of metal, lightsabers have something kind of like a laser beam for the blade. This beam is very powerful, and can cut through almost anything.

The lightsaber's blade can be red, blue, green, or purple. The Sith usually have red lightsabers, and the Jedi have the other three colors. In some of the Expanded Universe books, there are lightsabers that are other colors too.